Flame retarding solution and method for treatment of cellulosic materials therewith



United States Patent 2,728,691 FLAME RETARDING SOLUTION AND METHOD FOR TREATMENT OF CELLULOSIC MATERIALS THEREWITH Harry H. Beacham, Plainfield, and Irene M. Panik, Elizatreatment of cellulosic the necessary properties to be able to Withstand the rigors of handling and cleaning, particularly of washing andlaundering. Some of the known treating agents are capable of being washed and laundered to a limited degree, but most of them appreciably alter the appearance, texture or tensile strength of the treated. cellulosic ma terial. In addition many of the known agents are not suificiently adherent and tendto separate from the treated material in the form of fine dust.

Among the fire-retarding agents which are non-launderable are the alkali phosphate, borate and sulfamate types. Launderable types of agent include resins, chlorinated resins or waxes added in combination with inorganic oxides, such as antimony oxide. They, however, have the disadvantage of altering the appearance of the material considerably, and that they must be added in large quantity. Titanium has been added in several fireresistant processes, but in most of these the titanium has been added as titanium dioxide in order to' obtain opaque pigment efiects.

An object of this invention, therefore, is to provide a treating agent suitable for rendering fibrous cellulosic material fire-resistant. Still another object is to provide an agent for treating fibrouscellulosic materials to impart flame and glow resistant properties thereto which More specifically it relates to the treatment of will not be affected by washing or laundering. A further object is to produce an agent forrendering fire-resistant fibrous cellulosic materials in which the appearance, texture and tensile strength of the materials have not been altered by the treating agent. These and other objects of the present invention will become apparent as the invention is more fully' described. 1

In its broadest aspects this invention contemplates a flame-retarding solution for rendering fibrous cellulosic materials fire-resistant or non-inflammable, said solution comprising an aqueous solution of tetravalent titanium' chloride and trivalent titanium chloride. In particular,

this invention contemplates basic solutionsof the type described. This invention further contemplates production of a fire-resistant cellulosic material by impregnating the same with such a solution, gelatinizing said solution on said material to form a transparent gel, alkalizing said gel-containing material with an alkaline neutralizing agent, and subsequently washing and drying said material.

For improved flame resistance and resistance to afterglow, the titanium tetrachloride and trichloride solution may advantageously also contain antimony chloride and this improved solution is also contemplated by the present invention.

Although substantially any soluble chloride or mixture of'soluble chlorides of tetravalent titanium may be-used in the practice of the presenrinvention, it is preferred to so adjust the composition of the solution that there will be present at least 0.75 part of chloride (Cl") for each .part of titanium (calculated as Ti), since solutions containing less'chloride tend to be unstable in extended storage. On the other hand, solutions containing more than about 2.25 parts of chloride for each part of titanium are undesirable for use in connection with most cellulosic textiles, since they tend to exert a tendering action. In applications where tendering is not harmful, such as in the flameproofing of wood flour for example, or in textile applications where tendering is not objectionable, amount of chloride up to 3.0 parts chloride per part of titanium (the amount corresponding to normal TiCl4, approximately), or even higher amounts of chloride may be employed if desired. These values for the chloride content refer only to the chloride associated with the tetravalent titanium, and are in addition to the chloride values of the trivalent titanium chloride and, if present, antimony trichloride. The amount of tetravalent titanium chloride present in the solution may vary widely, but it is particularly desirable to have present in the solution amounts from about 50 grams per liter to about 150 grams per liter calculated as titanium.

From what has been said above regarding the amount of chloride values which should be associated with the tetravalent titanium, it will be seen that the preferred solutions for most purposes contain less chloride than corresponds to normal titanium tetrachloride. Such solutions may be produced in a variety of ways which will suggest themselves to anyone skilled in titanium chemistry. For example, titanium tetrachloride and bydrous titanium oxide may be employed in the proper proportions to provide a solution having the desired TizCl ratio, or titanium tetrachloride and antimony oxide may be employed to give solutions having less than the amount of chloride corresponding to TiCli and SbCls. Alternatively one may, if desired, use titaniferous starting materials which contain less chloride than does TiCl4, such as basic chlorides or partially-substituted chlorides.

With respect to the amount of trivalent titanium chloride which is employed in conjunction with the tetravalent titanium chloride, it has been found desirable to employ amounts from about one gram per liter to about 100 grams per liter calculated as TiCl3. For most types of cellulosic materials it is particularly desirable to employ trivalent titanium chloride in amounts from 5 grams per liter to grams per liter calculated as TiCls.

While no theory is postulated regarding the actual distribution of chloride ions with respect to triand tetravalent titanium ions, or other ions, if such are present, it has been found desirable, in order to facilitate understanding of the invention, to adopt the convention of considering the trivalent titanium to be completely saturated with respect to chloride ions (i. e. 3 mols of chloride for each mol of trivalent titanium, or 2.22 parts by weight of chloride for each part by weight of trivalent titanium), and accordingly, the amounts of trivalent titanium with its associated chloride values are herein expressed simply as parts of TiCls. Similarly, the amounts of antimony, with its chloride values, are expressed simply as parts of SbCls. The remaining chloride values present in solution are considered as being associated with the tetravalent titanium, and are expressed as parts of chloride (Cl-) for each part of tetravalent titanium, the tetravalent titanium values themselves being expressed as parts of tetravalent titanium and calculated as Ti.

The amount of antimony trichloride which may be added to the flame retarding solution for particularly desirable results may also vary widely. It has been found that the antimony trichloride should be present in an amount up to about 7.5 parts of SbCl3 for each part of tetravalent titanium, the preferred range lying between 1.5 and 5.5 parts of SbCls for each part of tetravalent titanium.

Fibrous cellulosic materials, which may be rendered fire-resistant by the process of the instant invention, in clude 'fabrics such as cotton, linen, regenerated cellulose such as viscose, cuprammonium, and cellulose acetate Patented Dec. 27, 1955 about /2 to A of its original weight.

or carbonate are preferred.

rayons, also natural fibers such askapok, hemp, wood and wood products such as pressed board, cardboard, batting, paper, Wood flour, sawdust and the like. The cellulosic material is treated with the titanium salt solution by any convenient means such as by dipping the material in the solution or by spraying the solution on the material. Any excess solution on the cellulosic material may 'be removed, for example, by squeezing between rolls, deliquoring in a centrifuge, or by any other appropriate method, depending upon the physical nature of'the material. It is preferred to leave a quantity of solution on the material about equal to the weight of the material itself, i. e., a Weight pick-up of about 100%. The titanium salt solution impregnated in the cellulosic material is gelatinized, for example by exposing the treated material to the atmosphere for a short interval of time. Satisfactory results have been obtained when the exposure is such as to reduce the Weight of solution held by the cellulosic material to The cellulosic material containing the gelatinized'treating'agent is then subjected to an alkalizing agent in order to raise the pH of the treated material to above 7.5, preferably above 9.0,

but not exceeding 12.0. The type of alkalizing agent used is unimportant although weak alkalizing agents such as, for example, sodium carbonate or ammonium hydroxide Ithas been found to be desirable, although not essential, to use alkalizing solutions which contain small amounts of soluble silicates, such as the alkali silicates, since these agents increase the efficacy of the treatment and contribute toward improved resistance to afterglow. The material is then rinsed well with water, for example by decantation, in order to remove the soluble salts therefrom, and is subsequently dried.

It has been found that the preferred amount of impregnant on the final material (dry basis) is about 7% to 14% of the weight of the fibrous cellulosic material when the basic tetravalent titanium chloride and trivalent titanium chloride are used alone, while about 15% to 30% is preferred when the combination of basic tetravalent titanium chloride, trivalent titanium chloride and antimony triehloride is employed. The entire process may be carried out at room temperature although if desired, higher temperatures may be employed.

It has been found that the amount of, trivalent titanium chloride may vary depending upon the type of the cellulosic materials to be treated. With respect to cellulosic fabrics, it has been found particularly desirable to use small amounts of trivalent titanium chloride in the solution for treatment of light weight materials lower than 6 oz. per square yard, such as, for example organdy,'marquisette, poplin, cotton fiannelette, broadcloth, muslin, damask linen, and regenerated textile'fabrics and the like.

For such materials it is convenient but not particularly necessary to employ amounts of trivalent titanium chloride from about 1 g. p. l. to g. p. l. calculatedas TiCla. For

medium weight fabrics such as those with weights of 6-10 ounces per square yard, which include oxford weave, twills, denim, ticking, velveteen, corduroy and the like, it is particularly'desirable though not essential to use trivalent .titanium chloride in amounts from 25 to 65 g. p. 1. calculated as TiCla in the treating solution. For heavy weight fabrics, such as duck, canvas and hemp, it .is desirable though not particularly necessary to employ trivalent titanium chloride in amounts about 65 g. p. 1. calculated as TiClz in the treating solution.

The exact nature of the physical and chemical changes that take place during the treating process is not completely understood; however, the titanium valuesin the treating solution are apparently converted toa transparent gel which adheres tenaciously to the cellulosic material and is not removed by subsequent washing. It may be held in the pores or between the fibers of the cellulosic material,

may be absorbedor adsorbed on the surface, or may react to some extent with the cellulosic materials. The

contribution, of the trivalenttitanium apparently results, at least in part, from its effect upon the structure of the cellulosic fiber. Titanium triehloride appears to act as a swelling and penetrating agent, and opens up the structureof the cellulosic fiber, allowing easier and more thorough impregnation of the fiber by the tetravalent titanium chloride. Photomicrographic examination supports this hypothesis, showing that when tetravalent titanium chloride alone is used, the titanium values are concentrated upon the surface of'the fiber, whereas when the combination of tetravalent titanium chloride with titanium trichloride is employed, the titanium values appear to be more or less uniformly dispersed throughout the fiber. Titanium .trichloride when employed alone, still exhibits this penetrating action and upon oxidation of the trivalent titanium values .to thetetravalent. state, exhibits a considerable degree of flameproofing action. However, since it is difficult to completely oxidize the trivalent titanium values, without either completely drying the cloth or employing strong, harsh oxidizing agents, it ispreferred to supply a portion of the titanium in the tetravalent state. Thus'the trivalent titanium values render the fiber susceptible of easy penetration by the tetravalent titanium values, and the tetravalent titanium values, whether originally present as such or derived by oxidation from the trivalent titanium, are believed to function as the principal fiameproofing agent.

In order to-more fully illustrate preferred embodiments of this invention, the following examples are presented:

EXAMPLE I An aqueous solution containing 51 g. p. 1. tetravalent titanium chloride calculated as Ti and containing 1.6 parts of chloride, calculated as Cl, for each part of titanium, and 29 g. p. 'l. trivalent titanium chloride calculated as TiCl3 were placed in a vessel. The tetravalent titanium chloride was obtained by adding 1 part of titanium tetrachloride to 5 parts of ice water over a period of /2 hour withrapid agitation to keep the temperature below and subsequently adding sufficient hydrous titanium oxide pulp, to reduce the amount of chloride present for each part of titanium to the amount above specified. The trivalent titanium chloride was prepared by electrolytic reduction of TiCl4 in the cathode chamber of an electrolytic cell having an aqueous HCl electrolyte and a porous diaphragm to isolate the cathode chamber. This solution was used for treating cloth.

The cloth was cotton twill weighing 8.2 ounces per square yard. The cloth was immersed in the solution for two minutes and was passed through a hand w'ringer. The immersing and wringing operation was repeated to obtain thorough soaking. The treated cloth was then partially dried by exposing the cloth to the atmosphere for 1 /2 hours at room temperature to gelatinize the treating agent on the cloth. 'The gelatinized cloth was then immersed for ten minutes in a solutionof sodium carbonate and sodium silicate to alkanize the solution containedon the cloth. The pHof the retainedsolution held by the cloth was 9.5. The excess solution was squeezed out of the cloth .by passing the cloth through a hand wringer. The cloth was thenwashed well with water until the retained solution had a pH of 8.0 and was then thoroughly dried.

The entire treatment procedure was carried out at room temperature. The treatedr cloth was subjected to standard flame tests and the results are recorded in Table 1.

Among the standard flame tests employed for the evaluation of thefiameproofing eflectiveness of the various so- .lutions tested were the 4S-microburner test and the vertical Bunsen burner test. The 45 microburner test consistsof exposing .thesmooth side of the fabric at an angle of 45, %1 inch above the top of the burner. The flame, 1% inches in length, is played on the fabric for 12 seconds. Theextent of the charred area is recorded,.as well as the afterfiaming and afterglow data in seconds. The

, procedure and apparatus assembly has been developed by the Quartermaster Corps of the United States Army and is described in Flameproofing TextileFabrics, by Major Robert W. Little (Reinhold Publishing (30., 1947, pp. 117-119). p 1

. 'Another test used in the evaluation of flame-resistance was the vertical Bunsen burnertest, which is carried out as follows:

The sample being tested is suspended vertically inch above the top of a Bunsen or Tirrill gas burner. The flame height is regulated to 1% inches with the air supply completely shut off. The resulting flame is luminous and non-waving. Theflame is applied vertically in the middle of the lower end of the specimen for 12 seconds and then withdrawn. The afterflaming in seconds is recorded. The specimen remains in place to determine afterglow which is also noted in seconds and the length of resulting char is measured. The charis measured by inserting hooks in the lower portion of the specimen, one on each side of the charred area, supporting a given weight on one hook and slowly raising the other. The char length is defined as the distance from the lower edge of the specimen to the extremity of the tear produced.

The test is widely used and is the test employed by the United States Bureau of Standards, the National Fire Protection :Association, United States Government agencies, American Society for Testing Materials and the National Research Council of Canada and is also described in Flameproofing Textile Fabrics, by Robert W. Little, Reinhold Publishing Corporation, 1947, pages l1ll15.

EXAMPLE II Another solution contained 51 g. p. l. tetravalenttitanium chloride calculated as titanium in which there were 1.6 parts-of chloride for each part of titanium, 29 g. p. l.

.trivalent titanium chloride calculated as'TiCla and 203 g. p. l. of antimony trichloride. This solutionwas used for treating another portion of the same cloth described in Example I. The treatment procedure employed was substantially the same as described in Example I. The treated cloth was subjected to the standard flame tests described under Example I and the results are recorded in Table I.

Atte'rflame (see.) Afterglow (see), Char Area (sq. in.) Vertical Bunsen burner test:

Atterflame (sea) After low (see) Char; ength (in) Tensile Strength Loss (percent Hand Appearance g very good Testing Solution Table I clearly illustrated that flame resistantproperties are imparted to clothtreated'witha solution containing tetravalent titanium chloride and, trivalenttitanium chloride when used alone or, in combination with antimony trichloride; when tetravalent titanium chloride and trivalent titanium chloride are used in a combination with the antimony trichloride the cloth also exhibits glow-resistant properties. EXAMPLE HI A solution containing 230 'g. p. l. titanium tetrachloride, i. e. 5 8 g. p. l. of'tetravalent titanium and about 3 parts of chloride for each part of titanium, and 12 g; l. titanium trichloride was used to treat broadcloth. The same procedure described in Example I was employed to treat the cloth and similar results to those shown .in Example I Were obtained, except that aloss of about 25 in tensile strength was sustained. i

EXAMPLE IV A A solution containing 45.5 g. p. l. of tetravalent titanium, for each part of tetravalent titanium approximately 1.5 parts of chloride, and 95 g. prl. trivalent titanium chloride was prepared. This solution was used EXAMPLE V A solution similar to that shown in Example III was used to treat Wood flour. The wood flour was immersed in the solution and agitated for ten minutes to insure thorough soaking. The excess solution was separated from the wood flour by deliquoring on a filter press. The filter cake was removed from themes and partially dried by three hours exposure to the atmosphere to gelatinize the solution on the wood flour.

This treated partially dried wood flour was then nexttralized with a solution of sodium carbonate and agitated for ten minutes to alkalize the solution on the wood flour. The wood flour was then deliquored and thoroughly washed in water. The treated wood flour was tested for flame retardancy by holding it in a flame of a Bunsen burner for several seconds. It was observedto char but not flame. Untreated Wood flour when tested similarly flamed immediately and was almost entirely consumed.

By means of the present invention it has also been found that fibrous cellulosic materials treated with a solution containing tetravalent titanium chloride and trivalent titanium chloride retained flame resistance. after laundering. The laundering is carried out in a tumbling chamber with 0.5% neutral soap solution at C. When the preferred method of this invention is employed utilizing the combination of tetravalent titanium chloride, trivalent titanium chloride and antimony trichloride as described, the superior flame and glow-resistant characteristics are retained even after repeated laundering. After six launderings, for instance, results are substantially equal to those before laundering.

These results are compared in Table II with a wellknown treating agent which consists of a mixture of borax, boric acid and diammonium hydrogen phosphate.

Table 11 45 Microburner Test vertical Burner Numher of gg After- Atter- Char Attet- Atter- Char g flame glow Area flame glow Length (sec.) (see) (sq. in.) (sec.) (sec.) (in.)

Tetravalent Titanium Chloride+fPrivalent Titanium Tetravalent Titanium chloride-l-Trivalent Titanium Chloride+Antimony Trichloride.

Do Borax+Boric A monium Hydrogen Phosphate 1 1 Completely burned.

As :shown in Table II fibrous cellulosic material when treated withasolutionof tetravalent titanium chloride and trivalent titanium chloride retains auseful measure favorable efiects 'upon flame and glow resistance, the

antimony trichlorideappears to have a beneficial effect upon'the resistance of the titanium compounds to removal by "laundering.

Recoveries of b'oth'titanium and antimony values are substantially 100% during processing. The amounts of titanium and 'antimony'originally absorbed on the fibrous cellulosic material are equal to the amounts retained in the final material after processing.

' 'When'the titanium values are present in cellulosic materials in substantiallyopaque form :the treated material has an unpleasant, chalky tone and a white dust may be continually renroved' fromthe-surface; When the process of'this invention is employe'dphow'ever, the titanium values are fixed -in the material in a form which does not substantially alter the appearance or texture of the material. The treatment'process is simple, convenient and economical to use. By employment of this invention fibrous cellulosic materials may be treated to render them substantially permanently .resistant to fire.

While this invention has been described and illustrated by the examples shown, it is not intended to bestrictly limited thereto and'oth'er modifications and'variations may be employed within the scope of the following claims.

We claim:

1. A solution for treatment of fibrous cellulosic materials to impart flame resi-stancethereto, comprising an aqueous solution of tetravalent titanium chloride and trivalent titanium chloride, said trivalent titanium chloride being present in amount from 1 g. p. l. to 100 g.-p. 1. calculated as 'TiCls, andin said tetravalent titanium chloride, said tetravalent titanium being present in amount from about .50 gap. 1. vto 150g. p. 1. calculated as Ti, the chloride values of said tetravalent titanium chloride being present in amount from about 0.75 to about 3.0 parts Cl for each partofTi, in addition to the chloride values of said TiCls.

2. A solution according vto claim 1, in which said chloride'valuesof said tetravalent titanium chloride are present in amount from about 0.75 to 'about-'2.25 parts Cl or each part of-"Ti in addition "to the chloride values -of said trivalent titanium chloride.

3.- A solution according to claim 1 in which said trivalent titanium chloride is present in amount from about 5 g. p. l. to about 75 g. p. 1., calculated as TiCls.

' 4. Asolution for-treatmentoffibrous cellulosic materials to impart flame resistance thereto, comprising an aqueous solution of tetravalenttitanium chloride; trivalent titanium chloride, and antimony trichloride; said trivalent titanium chloride beingpresent in amount from about .1. g. p. 1. to about 100 g. p. 1., said antimony chloride being present in amount up'to'about 7.5 parts SbCl3 for each part of tetravalent titanium, and in said tetravalent titanium chloride, said tetravalent titanium being. present in amount from about '50 to about 150 g. p. 1. calculated as Ti, the chloride values of saidtetravalent titanium chloride being present in amount from about 0.75 to about 2.25 parts Cl for each part of tetravalent Ti in addition to the chloride values of said trivalent titanium chloride and said antimony trichloride.

5. A solution according to claim 4 inwhich said antim'ony trichloride is present'inlamountfrom about 1.5 to about 5.5 parts SbCla for each part of tetravalent titanium.

6. process for treatment of fibrous cellulosic materials to impart flame-resistance thereto, which comprises impregnating said material with an aqueous solution-containing trivalent titanium chloride in amount from 1 to 100 grams per liter calculated as TiCl3 and tetravalent titanium chloride, said tetravalent titanium chloride being present in amount from 50 grams per liter to 150 grams per liter calculated as Ti, and the chloride values of said tetravalent titanium chloride being present in amount from about'0.75 to about 3.0 grams of Cl for each gram of Ti in addition to the chloride. values of said TiCla, partially drying said solution in said material by evaporation to the extent that the weight of the :solution retained in said material is reduced to between onehalf and one-fourth of its original weight, and alkalizing said solution in said material with an alkaline neutralizing agent.

References Cited in the file of this patent UNITED STATES PATENTS 2,570,566 Lane ..-Oct. 9, 1951 

6. A PROCESS FOR TREATMENT OF FIBROUS CELLULOSIC MATERIALS TO IMPART FLAME-RESISTANCE THERETO, WHICH COMPRISES IMPREGNATING SAID MATERIAL WITH AN AQUEOUS SOLUTION CONTAINING TRIVALENT TITANIUM CHLORIDE IN AMOUNT FROM 1 TO 100 GRAMS PER LITER CALCULATED AS TICL3 AND TETRAVELENT TITANIUM CHLORIDE, SAID TETRAVALENT TITANIUM CHLORIDE BEING PRESENT IN AMOUNT FROM 50 GRAMS PER LITER TO 150 GRAMS PER LITER CALCULATED TI, AND THE CHLORIDE VALUES OF SAID TETRAVALENT TITANIUM CHLORIDE BEING PRESENT IN AMOUNT FROM ABOUT 0.75 TO ABOUT 3.0 GRAMS OF CL FOR EACH GRAM OF TI IN ADDITION TO THE CHLORIDE VALUES OF SAID TICL3, PARTIALLY DRYING SAID SOLUTION IN SAID MATERIAL BY EVAPORATION TO THE EXTENT THAT THE WEIGHT OF THE SOLUTION RETAINED IN SAID MATERIAL IS REDUCED TO BETWEEN ONEHALF AND ONE-FOURTH OF ITS ORIGINAL WEIGHT, AND ALKALIZING SAID SOLUTION IN SAID MATERIAL WITH AN ALKALINE NEUTRALIZING AGENT. 